Keywords: attenuation, impact, damping, high speed, fastening system, railway.

Imperfections in the perimeter of the wheels and on the running surfaces of the rails, combined with irregularities in the support system of the track superstructure, are the cause of the presence of impact loads on the track. This dynamic effect increases with increasing speed. In superstructures consisting of concrete sleepers, the fastening element responsible for damping the forces applied to the rail and transmitted to the sleeper is the elastic pad. Therefore, one of the requirements demanded of this element will be a good damping capacity in order to achieve a better conservation of the track elements located below, as well as to improve the comfort in the vehicle's operation. The European standard EN 13146-3:2012 "Railway applications - Track - Test methods for fastening systems - Part 3: Determination of attenuation of impact loads", characterises the attenuation against impact loads of the support element. This standard sets out two possible procedures for determining attenuation, the so-called reference method and the alternative method. In both methods what is measured is the deformation of the sleeper when it is hit by a particular impact and the difference between methods lies in how the sleeper is placed. In the reference method, the sleeper rests on a ballast bed, without any additional load, while in the alternative method, the sleeper rests on an elastomeric mat of similar rigidity as the ballast and an additional load is applied to the system. The problem arises when carrying out an intercomparison between two laboratories in which the results differed by more than 100%. When analysing the results, it is verified that the test methods used are different and from this moment a research project begins by LADICIM, trying to justify this difference in the results. The objective of this paper has been to verify that the two methods proposed by the Standard are not equivalent, so it may be necessary to reconsider the Standard to avoid possible errors in determining the attenuation of rail fastening systems.

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